The gastrointestinal tract harbours approximately 1014 microbial cells, consisting of over 1000 species or phylotypes, the majority of which reside in the colon (Rajilic-Stojanovic and de Vosm 2014; Qin et al. 2010; Egert et al. 2006). The large intestine is a metabolically active site of fermentation, characterised by diverse and intricate microbial relationships that are integral to human health (Backhed et al. 2005). Experimental data have shown the extent to which the colonic microbiota and its human host exist in a delicate state of equilibrium. The microbiota has been shown to be associated with a wide range of health benefits including improved immune function and maturation, modified behaviour, regulation of satiety, inhibition of pathogens, augmentation of mineral absorption and maintenance of energy balance (Geurts et al. 2014; Parnell and Reimer 2012; Bravo et al. 2011; Buffie and Pamer 2013).
This host-microbiota interdependency has been illustrated in a study using mice and zebrafish, where the native microbiotas of each were transplanted into germ-free representatives of the other species. It was found that the composition would revert back to resemble that of the native host microbiota (Rawls et al. 2006). Imbalances in microbial community composition caused by diet, genetics, age, stress, or xenobiotics can induce a state of dysbiosis that may promote a more disease susceptible microbiota. Consumption of certain types of dietary components has a major influence on the communities of colonic microorganisms, with changes typically being observed within 24 hours of consumption (Wu et al. 2011; Parkar et al. 2012).
In the human gastrointestinal tract, Faecalibacterium prausnitzii is one of the most populous species, being typically observed at over 5% of the total proportion of the colonic microbiota of healthy adults (Miquel et al. 2013). Members of the Firmicutes phylum, F. prausnitzii are commensal inhabitants of the human large bowel, with demonstrated anti-inflammatory properties in vivo (Sokol et al. 2009; Furet et al. 2010). Low levels of F. prausnitzii have repeatedly been associated with a range of intestinal disorders including irritable bowel syndrome (IBS), atopy, diabetes and inflammatory bowel diseases (IBD) such as Crohn's disease (CD) and ulcerative colitis (UC) (Sokol et al. 2009; Furet et al. 2010; Rajilic-Stojanovic et al. 2011; Candela et al. 2012; Willing et al. 2010). These consistent observations show that a depleted concentration of F. prausnitzii is an undesirable endpoint and therefore any treatment that can selectively stimulate its proliferation is likely to be worthwhile.
The mechanisms by which F. prausnitzii facilitate their health promoting effects have been attributed to butyrate production and anti-inflammatory effects. A mouse study by Sokol and colleagues found that F. prausnitzii or F. prausnitzii supernatant reduced the severity of chemical-induced colitis, promoted the synthesis of anti-inflammatory cytokines, and mitigated proinflammatory cytokine production, suggesting that the anti-inflammatory effects are mediated by secreted metabolites (Sokol et al. 2008). In addition, F. prausnitzii generate large amounts of butyrate as well as some lactate and formate as the result of carbohydrate fermentation (Duncan et al. 2002; Duncan et al. 2004).
Constipation is a common condition which can significantly affect an individual's quality of life, with impairment being compared to that of serious chronic conditions such as diabetes and osteoarthritis. It is estimated that up to 20% of the world's population suffer from this condition, with women and individuals aged over 65 years being most frequently affected (Attaluri et al. 2011; Udani & Bloom 2013). Complications that can arise from constipation include anal fissures, rectal prolapse, and faecal impaction. Straining to pass stool may lead to hemorrhoids. In later stages of constipation, the abdomen may become distended, hard, and diffusely tender. Severe cases may exhibit symptoms of bowel obstruction, for example, vomiting and a painful abdomen, as well as encopresis, where soft stool from the small intestine bypasses the mass of impacted faecal matter in the colon.
It is well known that the disturbance of the microbiota balance in the digestive tract may change intestinal motility, resulting in constipation (Husebye et al, 2001; Rhee et al. 2001). In addition, patients with chronic intestinal constipation present imbalance in the microbiota, characterized by a relative decrease of beneficial bacteria and an increase of potentially pathogenic bacteria and fungi (Khalif et al. 2005). Such patients show a significant increase in the counts of E. coli, S. aureus and enterobacteria (Khalif et al. 2005).
Moreover, a longer disease progression of chronic constipation leads to higher scores for undesirable microorganisms, and the lower scores for desirable ones (Khalif et al. 2005). In a study with children diagnosed with chronic constipation, intestinal dysbiosis was found in the faeces, with a significant increase in the counts of Clostridium, Bacteroides, and E. coli (Zoppi et al. 1998). One particular study has found a significant decrease in the count of Bifidobacterium and Lactobacillus strains in faeces of constipated individuals; such decrease is up to ten times lower for the Bifidobacterium genus (Chassard et al. 2012).
The intervention options for constipation remain difficult and challenging, and many individuals are dissatisfied with current therapies and medications. These include lifestyle and dietary modifications such as increased consumption of fruit and vegetables, fibre supplementation (methylcellulose; Konjac glucomannan, psyllium), increased fluid intake and exercise, as well as pharmacological intervention with stool softeners, stimulant laxatives and osmotic laxatives (Attaluri et al. 2011; Leung et al. 2011; Liu 2011).
The routine use of laxatives is contraindicated, as patients may come to be dependent upon their use. Enemas can be used to provide a form of mechanical stimulation. On the other hand, enemas are typically useful only for stool in the rectum, not in the intestinal tract. An increasing range of herbal and other natural products (including aloe and rhubarb (Udani & Bloom 2013)) advertised for aiding laxation have been made available on the market. Yet, there is only anecdotal evidence regarding their efficacy and success in affording relief from constipation.
By contrast, fibre is well known to be important in digestion—soluble fibre attracts water helping to slow digestion, and insoluble fibre adds bulk to stool to assist laxation. Enzymes also aid digestion by breaking down the large dietary compounds into smaller manageable pieces. For example, amylase breaks down starch into simple sugars and proteases break down proteins into amino acids. However, fibre and enzyme supplementation alone are largely ineffective for slow-transit constipation (prolonged delay in the transit of stool through the colon) and defecatory disorders. In addition, such supplementation may have unwanted side-effects such as excessive gas production and uncomfortable bloating.
Green kiwifruit (e.g., Actinidia deliciosa var. Hayward) have been highlighted as an effective product in the area of digestion with several studies now demonstrating their efficacy (Stonehouse et al. 2012). The current consensus is that the laxation effect of green kiwifruit appears to be primarily due to its dietary fibre and actinidin (enzyme) content (Chang et al. 2010; Rush et al. 2002, Stonehouse et al. 2012, Drummond & Gearry 2013).
In contrast, gold kiwifruit (e.g., Actinidia chinensis var. Hort16A) are not traditionally associated with laxation (Ferguson 2003; Rush 2002). It has been noted that gold kiwifruit has little/no actinidin content and less dietary fibre than green kiwifruit. The Hort16A variety of kiwifruit has been investigated for its effect on immunity (Hunter et al 2012; Skinner 2012), with the contention that the reduced or lesser laxative effects of gold kiwifruit make it an ideal choice for naturally boosting immunity, particularly in children where increased laxation may not be desirable (Adaim 2010).
Given the occurrence of gastrointestinal disorders in the population, there is a need for new compositions, particularly compositions derived from natural sources, for restoring and maintaining digestive health.